1. Field of the Invention
The invention relates to antimicrobial agents, products incorporating such agents, and methods of making such products. More particularly, the invention relates to polymer-based antimicrobial agents.
2. State of the Art
Silver and silver salts are commonly used as antimicrobial agents. An early medicinal use of silver was the application of aqueous silver nitrate solutions to prevent eye infection in newborn babies. Silver salts, colloids, and complexes have also been used to prevent and to control infection. Other metals, such as gold, zinc, copper, and cerium, have also been found to possess antimicrobial properties, both alone and in combination with silver. These and other metals have been shown to provide antimicrobial behavior even in minute quantities, a property referred to as “oligodynamic.”
Metallic antimicrobials function by releasing metal ions into the microbe. The released ions react with protein and other anions (negative charged species) in the microbe and render the protein insoluble and thereby inactive. The inactive protein perturbs cellular function, disrupts membranes and prevents the normal activity and reproduction of DNA thereby essentially killing the microorganism.
U.S. Pat. No. 6,306,419 to Vachon et al. discloses a polymer-based coating comprising a styrene sulfonate polymer with a carrier molecule bound to silver ion incorporated therein. The styrene sulfonate polymer is prepared by reacting an acetyl sulfate sulfonation agent with a styrene copolymer in 1,2-dichloroethane (DCE). The coating is hydrophilic such that it retains a relatively large amount of water or water-containing fluid. There are several disadvantages to this composition. One such disadvantage is that larger quantities of the silver metal are required to provide effective antimicrobial activity. A second disadvantage is that the carrier molecule is required which renders it more expensive as well as more difficult to dispose of the carrier byproduct. A third disadvantage is that a solvent other than water (e.g. DCE) is required to prepare the polymer matrix. Such solvents are typically hazardous because of their reactive nature and thus require special care in handling and disposing of such solvents, which limits the widespread acceptance of such antimicrobial polymers in many applications.